kin recognition / blue-footed booby at its nest, delineated by the "guano ring"

Information caption

Kin selection depends on organisms being able to differentiate kin from non-kin (Grafen 1990). Since they cannot determine each other's genes directly, kinship or degree of genetic relatedness must be perceived indirectly, through vicarious clues (Campbell 1974). For example, blue-footed boobies on the Galápagos Islands (Sula nebouxii) recognize their offspring only by location: within a ring of guano that marks their rudimentary nest. If a nestling falls outside the ring, whether accidentally or by being pushed, it is treated as non-kin and is neither cared for nor permitted to return (Gould 1983). Vicarious indicators, one may note, do not always function optimally.

Inquiry caption

Kin selection can only be effective if organisms can differentiate kin from non-kin (Grafen 1990). Since they cannot determine each other's genes directly, kinship or degree of genetic relatedness must be perceived indirectly, through vicarious clues (Campbell 1974). In what ways might organisms be able to identify or detect kin, directly or indirectly? [Students list possibilities.]

Here are a few examples. In the case of Belding's ground squirrels, locality itself may function as a substitute when kin tend to inhabit the same area. Boobies on the Galápagos Islands (Sula nebouxii), pictured here, also recognize their offspring only by location: within a ring of guano that marks their rudimentary nest. If a nestling falls outside the ring, whether accidentally or by being pushed, it is treated as non-kin and is neither cared for nor permitted to return (Gould 1983).
Target Concept: Organisms can determine kin relatedness in many ways, sometimes by indirect cues.